Quiz 6 - Make up

Question 1

What is the electron transport chain (physically speaking) and what is its function?

Answer 1

The ETC is a series of 4 protein complexes embedded in the inner mitochondrial membrane (eukaryotes) or plasma membrane (prokaryotes)

Question 2

What donates electrons to the ETC?

Answer 2

NADH

Question 3

Why move electrons through the ETC (what is the overall purpose of doing this)?

Answer 3

The purpose is to transfer energy

Question 4

What is the final electron acceptor at the end of the ETC (during AEROBIC respiration)?

Answer 4

Oxygen

Question 5

What gets shuttled across the membrane as electrons move?

Answer 5

H+ ions

Question 6

How is ATP made at the end of the ETC? What powers the enzyme complex that makes the ATP? How many ATP are typically made? What is meant by oxidative phosphorylation?

Answer 6

• ATP is made by chemiosmosis at the end of the ETC
• ATP synthase is the enzyme complex
• Oxidative phosphorylation uses oxygen reduction to generate ATP
  – 32-34 ATP typically made

Question 7

Anaerobic respiration
- How is it similar to aerobic respiration (e.g. what steps are similar)? How is it different?
- Why is less ATP made?

Answer 7

Both utilize glycolysis as the starting step, and both produce ATP, although anaerobic respiration produces less ATP because there is less e- movement, meaning less H+ shuttling (and therefore less ATP)

Question 8

Anaerobic respiration
- What typically serves as electron acceptors in place of oxygen? Why not use oxygen here?

Answer 8

• Alternative receptors such as NO3, SO4, and Fe2+
• O2 cannot be used as the final electron acceptor bc some material species are killed by O2, others lack certain needed enzymes, or may be missing a complete ETC

Question 9

Fermentation
- How is it different from both forms of respiration described above?
- What is its broad purpose?

Answer 9

Fermentation is an alternative to respiration that does not use ETC or Kreb’s cycle (also occurs in the cytosol)
- Electrons from NADH are put back into pyruvates to regenerate NAD+ (which is needed for future glycolysis)

Question 10

Fermentation
- What happens to pyruvate?
- How many ATP does it generate?

Answer 10

• Pyruvate is converted into other organic compounds (lactic acid, CO2, etc.)
• no additional ATP made (only 2 from glycolysis)

Question 11

Fermentation
- What is the difference between lactic acid and alcohol fermentation in terms of the reactions and products?

Answer 11

Lactic acid fermentation - pyruvate is reduced with e- from NADH and help from enzyme lactic dehydrogenase

Alcohol fermentation - pyruvate loses a CO2 and becomes acetaldehyde, and alcohol dehydrogenase turns acetaldehyde into ethanol (NADH give e- -> NAD+)

Question 12

Fermentation
- Know some of the basics about the diversity of sugars used and diversity of products made (beyond glucose and alcohol/lactic acid respectively)

Answer 12

Microbes can ferment sugars other than glucose (ex. lactose, maltose, sorbitol, etc) giving different end products

Different species have different fermenting abilities (can use for identification)

Question 13

Lipid catabolism
- What are fats broken down into and how are those intermediates further broken down?

Answer 13

Fats are broken down into fatty acids and glycerol
– fatty acids oxidized into acetyl CoA, which enters Kreb’s cycle
– glycerol converted into G3P, which enters glycolysis

Question 14

Protein catabolism
- What are fats broken down into and how are those intermediates further broken down?
- How are those smaller breakdown products used to generate ATP (is there a separate lipid pathway?)

Answer 14

Extracellular proteases digest proteins into individual amino acids
– amino acids are modified into organic compounds that can enter the Kreb’s cycle

Question 15

Chemoorganotrophs

Answer 15

obtain energy through the breakdown (oxidation) of organic compounds

Question 16

Chemolithotrophs

Answer 16

obtain their energy through the oxidation of inorganic ions or compounds

Question 17

Phototrophs

Answer 17

use light as an energy source to drive photosynthesis

Question 18

Acquiring energy
- What types of molecules get oxidized for organo vs litho? How does that oxidation lead to ATP generation? (hint: has to do with electron transport chains and ATP synthase)

Answer 18

Organo - oxidize sugars, proteins, and lipids to make ATP (use standard glycolysis, Krebs, and ETC)

Litho - oxidize chemicals like H2 gas, H2S, NH3, and more (e- are extracted and sent to an ETC, where an H+ gradient is created and ATP synthase is activated)

Question 19

How do phototrophs generate ATP?
You need to review the basic steps of the light reactions and dark reactions of photosynthesis.

Answer 19

Use light as an energy source to drive photosynthesis
– H+ concentration gradient created as e- move and ATP is made by ATP synthase
– ATP and NADPH is then used in dark reactions to make glucose

Question 20

Know the difference between oxygenic and anoxygenic photosynthesis as it pertains to photolysis. Why do photolysis? Why do some organisms release O2 and some don’t? Review some of the types of organisms that use oxygenic vs anoxygenic photosynthesis.

Answer 20

Oxygenic photosynthesis : get their electrons from water via photolysis
- O2 is released
- organisms – cyanobacteria, algae, plants

Anoxygenic photosynthesis: get their electrons from other atoms/molecules like H2S and Fe2+
- O2 is not released
- organisms – heliobacteria, purple sulfur bacteria

purpose of photolysis is to gain electrons

Question 21

Acquiring carbon
- What is the difference between an autotroph vs a heterotroph? Would phototrophs, chemolithotrophs, and chemoorganotrophs be classified as auto or hetero?

Answer 21

Autotrophs take carbon from atmospheric CO2
– incl. chemolithotrophs and most phototrophs

Heterotrophs take carbon from internalized macromolecules and convert it into other macromolecules
– incl chemoorganitrophs